A new book explores a legendary advisor who may have had the secret to success in Vietnam — and in winning today’s forever war.

Max Boot’s newest book chronicles the life and impact of Edward Lansdale, the famous American advisor and CIA officer sometimes hailed as the “Lawrence of Asia.” A near-legend alternately seen as a kingmaker or an oddball, Lansdale helped trailblaze one American approach to fighting communist insurgents during the early days of the Cold War — an approach that was soon scorned by policymakers at the top. Deeply researched and evenhanded, The Road Not Taken: Edward Lansdale and the American Tragedy in Vietnam is a superb scholarly achievement.

Boot, a historian and columnist for Foreign Policy, comes at Lansdale having already written two major books on small wars and counterinsurgency, a solid foundation that he takes to a new level here with rigorous research and dogged investigation into little-known corners of Lansdale’s life. He taps the most up-to-date scholarly sources, such as Lien-Hang Nguyen’s Hanoi’s War and Fredrik Logevall’s Embers of War, and his own primary research is most impressive. He conducted more than 20 interviews with people who knew Lansdale and visited more than 30 archives, including in the Philippines and Vietnam. He makes use of the most recently declassified material. And Boot is the first author to gain access to the letters Lansdale wrote to his wife and his Filipina lover (and future second wife), which reveal copious details about his thinking and motivation.

The thrust of Boot’s argument is that the United States missed an opportunity for a less traumatic outcome in Vietnam, and again in today’s long wars, by neglecting Lansdale’s example. Eschewing Lansdale’s deep local knowledge, trust with leaders, and skepticism of the value of large numbers of troops on the ground is, for Boot, the “road not taken.”

The argument is relevant both for America’s revisiting of Vietnam and for how it handles strategy today. Boot’s takeaway is that skilled advisors with a bias toward democratic reforms could have yielded better results not only in Vietnam but also in America’s more recent wars.

Edward Lansdale was a California advertising man who joined the fledgling Office of Strategic Services during the World War II, later going on to become a CIA officer and U.S. Air Force major general. He played a pivotal role on the Cold War battlefields of the Philippines and Vietnam, skillfully advising Philippine and South Vietnamese leaders wrestling with communist insurgencies. In his Vietnam masterpiece, A Bright Shining Lie, reporter Neil Sheehan called Lansdale a “legendary clandestine operative.” (For years, Lansdale was also rumored to be the model for Graham Greene’s The Quiet American, though Greene denied it, having written the book before Lansdale arrived in Vietnam.)

Lansdale’s greatest achievements — and the ones that point most clearly to the path that Boot thinks should have been taken — were helping then-Philippine Defense Minister Ramon Magsaysay defeat the Hukbalahap insurgency in the Philippines and then engineering Magsaysay’s 1953 presidential election. Lansdale then moved to Vietnam and deftly outmaneuvered the 1955 attempt to overthrow the South Vietnamese leader Ngo Dinh Diem. While critical of his many failings — detractors for years have suggested Lansdale was naive and morally corrupt — Boot makes clear that Lansdale had a unique gift for working with Filipinos and the South Vietnamese. He was the advisor par excellence.

Just what made Lansdale such a storied advisor lies at the heart of Boot’s book — and of the idea that his playbook could be applicable today. Lansdale had an intimate knowledge of the society, culture, politics, and history of the countries in which he worked.

He learned by leaving the bubble and taking the time and trouble to meet with as many people from diverse backgrounds as possible, in barrios, villages, and the countryside. In his first stint in the Philippines, for instance, Lansdale would head out nearly every weekend and crisscross the countryside, learning what locals cared about. In South Vietnam, he set out into the rural strongholds of the paramilitary religious sects, gaining a firsthand knowledge of leaders who would later try to overthrow the regime. That contrasts with the all-too-cloistered existence U.S. officials and officers often find themselves in while on assignment. And he put in the time: two deployments to the Philippines totaling almost seven years, and two deployments to South Vietnam for a total of more than five years. The total outstrips most Americans’ time on the ground in the recent wars.

Lansdale also had a unique ability to build trust, which underpinned the willingness of Philippine and South Vietnamese leaders to listen to his advice. Boot doesn’t shy away from the fact that Lansdale passed cash to his partners, such as during Magsaysay’s 1953 campaign for president. But money is not the whole story. Shared experience, patience, and genuine care for the well-being of his local partners mattered just as much. Lansdale and Magsaysay sometimes lived together and often traveled together, occasionally bouncing or flying recklessly through combat zones side by side.

“Comrades are listened to, when they share risk,” Lansdale later advised. With Diem, a much less charismatic partner, Lansdale had another weapon: the patience to simply listen to the long-winded leader and his ideas for hours on end. (Other Americans loathed Diem’s diatribes.) Probably as important, at a time when the French and other Americans were trying to undercut Diem, Lansdale had no intention to harm or remove him. There is no trust if a partner thinks an advisor is out to get him.

Remarkably, Lansdale spoke no foreign languages. It takes effort, but language itself builds trust. I cannot count the number of times an Afghan has told me how happy he was that I came to a meeting alone so that he could talk freely. America’s advisors and diplomats should seek to outdo Lansdale in that regard.

Boot argues that Lansdale’s talents as an advisor gave a better understanding of how to achieve progress in Vietnam than U.S. commanders in the field or senior leaders in Washington did. By ignoring Lansdale’s advice, Boot maintains, the United States lost opportunities to set the war on a less painful course: The decisions to build a conventional-style South Vietnamese army, to deploy large numbers of U.S. forces, and to forgo democracy all ran contrary to his counsel. Most egregiously, in 1963, Washington decided to overthrow Diem, a nationalist if flawed leader. Lansdale had warned that years of political chaos would follow, as indeed they did.

Lansdale was onto something. For all his flaws, Diem probably would have led a more stable, tougher government than the ones that followed his. In this environment, the United States may have been less compelled to deploy hundreds of thousands of soldiers and Marines. “At the very least the war’s loss would have been less painful all around if Lansdale’s advice had been heeded,” Boot writes. “He had never wanted to see half a million American troops thrashing around Vietnam, suffering and inflicting heavy casualties. His approach, successful or not, would have been more humane and less costly.”

Boot’s broader message is that skilled, locally savvy advisors could have yielded better results not just in Vietnam — but also in America’s more recent wars. A major shortcoming in Iraq and Afghanistan was the lack of on-the-ground leaders with Lansdale’s level of local knowledge and people skills, Boot contends. In his view, there was no Lansdale-like rapport with national leaders. In sharp contrast to Lansdale’s privileged ties to Magsaysay and Diem, the United States had poor relationships with Iraqi Prime Minister Nouri al-Maliki and Afghan President Hamid Karzai, and it could not dissuade them from bad decisions that ended up fueling support for insurgents and terrorists.

Based on my experiences as a civilian advisor in Afghanistan, I am inclined to agree that America did not always have the right people in place, with the best knowledge of the country and rapport, and those gifted with those characteristics — Ambassador Zalmay Khalilzad and Gen. Stanley McChrystal, for example — were around all too briefly. As in Vietnam, most leaders came and went on one-year tours. Those who learned among the people, as Lansdale had, were usually deemed too junior or unconventional to play a high-level role.

The mistakes U.S. leaders made, especially early on, were glaring. In Iraq, the United States de-Baathified the government, dissolved the army, and allowed sectarian strife to smother democracy. In Afghanistan, the United States rejected negotiations with the Taliban, built an army too slowly, permitted excesses by warlords, and caused too many civilian casualties. Washington misunderstood the Afghan people, the deep roots the Taliban had planted in society, and the likelihood they would sprout again.

The United States seemed deaf at times to local concerns, especially when it came to Karzai. Few Americans were willing to sympathize with Karzai or look out from his point of view. Critics seemed oblivious to popular support for Karzai and how much he hewed to traditional Afghan themes of independence and sovereignty. Over time, Karzai became increasingly resentful of Americans and resistant to sound advice. U.S. leaders did not listen to him, so he did not listen to them. It recalls Lansdale’s advice to President John F. Kennedy about Diem: “If the next American official to talk to President Diem would have the good sense to see him as a human being who has been through a lot of hell for years — and not as an opponent to be beaten to his knees — we would start regaining our influence with him in a healthy way.”

To his credit, Boot does not argue that Lansdale could have definitively turned around Vietnam, nor that following his model could have done the same in Iraq or Afghanistan. He acknowledges that larger factors were and are at play. In all three countries, the governments were beset by a degree of corruption and strong-arm tactics that even a good leader was unlikely to overcome. To take one example: In Iraq, more was going on than simply inaction by Maliki or the United States. Sectarian fears and friction inexorably drove Sunnis and Shiites apart — and drove Shiite politicians like Maliki to ill-advised lengths. Even Lansdale would have been hard-pressed to get Maliki to swim against that tide for long. Nor could good advisors much affect the cross-border safe havens of North Vietnam and Pakistan that endowed insurgents in South Vietnam and Afghanistan with an enduring strength and resilience.

Finally, I would underscore how in all three countries the adversaries were determined to fight foreign occupation. The United States should be mindful of how nationalism can inspire men and women to resist occupation and how an American presence — even if necessary — can discredit the very governments it’s trying to help. “Nationalism,” Samuel Huntington wrote, “is the cement of the revolutionary alliance and the engine of the revolutionary movement.”

Lansdale himself would probably argue that the Philippines and Magsaysay prove that decisive turnarounds are in fact possible. Yet the Philippines was a special case. Unlike Vietnam or Afghanistan, it was an archipelago physically isolated from communist supply and safe havens. And Lansdale got lucky with Magsaysay, a tireless former elected official, defense minister, and anti-Japanese guerrilla leader with a strong sympathy for the average Filipino and Philippine soldier. On top of everything else, we should remember that the U.S. military stayed in the Philippines for decades.

Lansdale’s love of the Philippines and Vietnam clouded his objectivity. He understandably wanted to save his Vietnamese friends from abandonment and death — a feeling familiar to many who have served in Iraq and Afghanistan. Perhaps he should have recognized his bias and held back from claiming the Vietnam War could be won. His road not taken was a better option. But withdrawal may have been the best.

An advisor cannot change the world. Lansdale’s tragedy is partly that he thought he could. Advisors can make a big difference. A well-placed one can prevent devastating failures and seize opportunities. They can help boost military effectiveness. But creating a state that can stand on its own and provide long-term stability without U.S. presence is something entirely different. One of Boot’s most telling passages is this:

The post-1953 tribulations of the Philippines showed how difficult it was to fundamentally transform a country, any country, whose social and political contours had been shaped by myriad factors over the course of a long history, like rocks formed by the accumulation of sediment over the millennia. Lansdale could accelerate and guide political change in the short term. Making that change last was a much more difficult proposition.

Lasting solutions to the intractable problems of failed states are, in my view, outside the power of an advisor and usually outside the power of the United States itself. The best U.S. leaders and policymakers should expect is that if they stay, they can manage problems and prevent outright failure or collapse. What advisors, even ones as gifted as Lansdale, are unlikely to provide is decisive success or a clear path out.

This article originally appeared in the January 2018 issue of FP magazine.

Carter Malkasian is the author of Illusions of Victory: The Anbar Awakening and the Rise of the Islamic State.